So I got my first level 4 unique named merchant - the scribe - working my armor store. No props there.

But anyone able to equip their level 4 merchants with gear you want them to use?

All settlers other than the doctor merchants can just be talked to anytime 24/7 to trade or barter - the former lets you trade and equip them, the latter buys from their store.

The doctor has no trade function during their working hours but after 8pm you can talk and get the trade conversation to equip them;

The level 4 merchant however, seems to always be in barter mode 24/7. I can't get the trade dialog in order to open their personal inventory and gear them out. Anyone find a way around this?

Have you tried pickpocketing him?

I made the Abernathy girl a doctor at the farm- I had to un-assign her and interact with her as a settler in order to equip her with a lab coat (and an assault rifle - lol) , and then re-assign her to the medic booth. She loses all of thet "I love to go shopping in Diamond City" dialogue and will only say the doctor lines, so I think you just need to un-assign him for a bit.